Just the words ‘barcodes’ or ‘QR codes’ inspire a certain paranoia among some people. Their uses are many, but until the Center for Land Use Interpretation (CLUI) published a recent report, not many Americans were aware of barcodes on the ground across the country.

These two-dimensional images were largely painted in the 1950s and ’60s for use by the Air Force and NASA to calibrate aerial cameras.

Still used today, the images are clustered around the Mojave Desert where they were likely employed by the A12, SR-71, and U-2 spy-planes that each used highly sophisticated and powerful cameras to spy on nations across the globe.